Aspergillus fumigatus is a spore forming mould that causes a range of human diseases, including allergic bronchopulmonary aspergillosis, an asthma-like disease, and invasive aspergillosis, a frequently fatal infection that occurs in immunocompromised individuals. Infection by Aspergillus fumigatus results from inhalation of fungal spores (referred to as conidia), which are taken up by alveolar macrophages and killed by products of the oxidative burst. Although A. fumigatus-specific T lymphocytes are postulated to play a role in both allergic and invasive aspergillosis, very little is known about their activation, proliferation, differentiation and persistence following inhalation of fungal spores. To address this issue, we made CD4 T cell hybridomas specific for A. fumigatus antigens, cloned the alpha and beta chains of the specific T cell receptor and generated T cell receptor transgenic mice. Experiments proposed in this grant application will useT cell receptor transgenic mice to obtain naive, A. fumigatus-specific T cells for transfer and characterization in infected recipient mice. We have three specific aims. The first is to investigate priming and differentiation of naTve A. fumigatus-specific T lymphocytes following pulmonary infection with live conidia. The impact ofii_10 and TGF-beta signaling on T cell proliferation and differentiation will be determined. The second aim is to determine the impact of A. fumigatus-specific CD4 T cells on invasive fungal disease in immunocompromised or bone marrow transplanted mice. Our third aim is to investigate innate immune responses to fungal spores and to determine the impact of this process on the differentiation of A. fumigatus-specific CD4 T cells. We will initially focus on MyD88, Trif and Rip2 mediated signals. These studies will provide a comprehensive picture of T cell responses to the most prevalent opportunistic fungal pathogen of humans, potentially opening the door to new therapeutic interventions to combat allergic and invasive fungal diseases.